Display devices including organic electroluminescence (EL) elements or liquid crystal elements have been used in various fields. A display device is constructed by stacking a plurality of members. In such a display device, there is a concern that a warp occurs due to a difference in thermal expansion coefficient between the respective members.
For example, as regards an optical sheet in which a plurality of optical elements, which are formed of materials with different thermal expansion coefficients, are adhered or attached, there is known a technique of reducing a warp by providing a warp prevention layer having a thermal expansion coefficient which is equal to a thermal expansion coefficient of an optical functional member. In addition, as regards an organic EL device configured such that a warp-reducing substrate, which is opposed to a light emission element provided on a substrate body formed of glass, and a warp-reducing substrate disposed on that surface of the substrate body, which is not opposed to the light emission element, are attached, there is also known a technique in which the two warp-reducing substrates are formed of materials having an equal thermal expansion coefficient, and the thermal expansion coefficient of the materials is close to the thermal expansion coefficient of the substrate body, thereby reducing a warp. Furthermore, as regards a semiconductor device in which a semiconductor chip is bonded on a substrate, there is known a technique in which a warp prevention sheet, which is bonded to the other surface of the semiconductor chip, and the substrate have substantially equal thermal expansion coefficients, thereby preventing a warp of the semiconductor device.